Measuring Crankshaft Bearing Clearances - Plastic Gage Method

Install the crankshaft bearings into the engine block.

Fig 1: Engine Block & Crankshaft Bearings
Courtesy of GENERAL MOTORS CORP.
Install the crankshaft.

Fig 2: Engine Block & Crankshaft
Courtesy of GENERAL MOTORS CORP.
Install the gaging plastic the full width of the journal.

Fig 3: Gaging Plastic Installed On Journal
Courtesy of GENERAL MOTORS CORP.
Install the crankshaft bearings into the crankshaft bearing caps.

Fig 4: Bearing Caps & Crankshaft Bearings
Courtesy of GENERAL MOTORS CORP.
Install the crankshaft bearing caps in the original positions and with the arrow on the crankshaft bearing caps in the direction of the front of the engine block.
Install the crankshaft bearing cap bolts.
Tighten

Tighten the crankshaft bearing caps to 105 N.m (77 lb ft).
Remove the crankshaft bearing cap bolts.
Remove the crankshaft bearing caps. The gaging plastic may adhere to either the crankshaft bearing journal or the crankshaft bearing surface.

Fig 5: Crankshaft Bearing Caps & Bolts
Courtesy of GENERAL MOTORS CORP.
Without removing the gaging plastic, measure the compressed width at the widest point using the graduated scale on the edge of the gaging plastic envelope.
If the flattened gaging plastic tapers toward the middle or the ends, there may be a difference in clearance indicating taper, low spot or other irregularity of the crankshaft bearing or the crankshaft bearing journal.
Remove the flattened gaging plastic.
Measure the remaining crankshaft bearing journals.

Fig 6: Measuring Compressed Width At Widest Point Using Gaging Scale Plastic Envelope Graduated Scale
Courtesy of GENERAL MOTORS CORP.